1. Field of the Invention
The present invention relates to a method for manufacturing a cylinder block for an internal combustion engine. More specifically, the present invention relates to a method of manufacturing a cylinder block with increased resistance to abrasive damage.
2. Description of the Related Art
There is a growing commercial demand for sleeveless cylinder blocks in internal combustion engines. Sleeveless cylinder blocks are preferably made from aluminum to reduce weight and improve engine cooling. Since aluminum sleeveless cylinder blocks are easily worn during use, a demand exists for cylinder blocks with an increased resistance to abrasion.
In response to the above demand, Japanese Unexamined Patent Publication No. 06-249057 has proposed a method for forming an abrasion-resistant layer on the inner surface of a cylinder by build-up welding. This Publication also describes a method for manufacturing an aluminum cylinder liner.
Unfortunately, the direct application of this build-up welding method to a cylinder block causes large welding strains due to the large thermal expansion coefficient of aluminum. The great welding strains caused by this method result in an unacceptable increase in the distortion in the cylinder block itself.
Large increases in cylinder block distortion make it nearly impossible to accurately position the cylinder block in a jig for post processing. This inability to accurately determine post processing distortion requires manufacturers to provide large finishing allowances thereby increasing costs. In some extreme cases, post processing causes the abrasion-resistant layers to crack or fail, making it impossible to use the cylinder block and further increasing costs.
The above-described method makes it practically impossible for designers to accurately predict the resulting strain distortion and the ultimate final shape further increasing costs, production times, and reducing quality. Other attempts to provide an abrasion resistant layer with high-composition aluminum alloy build-up welding have proven equally unsuccessful since the larger the composition of aluminum, the larger the resulting welding strain. In sum, the above-described method and others have not successfully met the commercial demand.
It is an object of the present invention to overcome the above-described liabilities.
It is another object of the present invention to provide a method where welding strain is effectively managed while forming an abrasion-resistant layer.
It another object of the present invention to provide a method for manufacturing a cylinder block where an abrasion resistant layer is formed by build-up welding, where build-up welding is overlaying and thickening of a material with a welding practice.
It is another object of the present invention to provide a method of manufacturing a cylinder block where build-up welding occurs on an inner bore surface of a cylinder in an area receiving abrasion during piston-action.
It is another object of the present invention to provide a method where build-up welding occurs in an area from at least about xc2x15xc2x0 to about xc2x185xc2x0, along a thrust direction of a piston, and in an area from at least about xc2x15xc2x0 to about xc2x185xc2x0 in an anti-thrust direction of the piston.
It is another object of the present invention to provide a method easily adaptable to a inner surface of a preformed semi-elliptical or semi-oval-shaped engine block.
It is another object of the present invention to provide a method which allows increased predictive accuracy of post-processing distortion.
It is another object of the present invention to provide a method which has the foregoing features and capabilities.
The present invention relates to a method for manufacturing a cylinder block providing an abrasion-resistant layer in a cylinder bore by build-up welding. The method applies build-up welding to preformed recesses along an inner surface of the cylinder bore. After build-up welding, final finishing provides a finished bore surface. The method provides an abrasion-resistant surface in areas prone to piston abrasion and manages welding strain to effectively minimize cylinder block distortion.
According to an embodiment of the present invention, there is provided a method for manufacturing a cylinder block of an internal combustion engine, comprising the steps of: defining a set of parameters for the cylinder block including at least an abrasion resistance layer thickness, a desired welding strain, a first finished bore dimension, a thrust direction, and an anti-thrust direction, preforming a cylinder block matching the set of parameters, designating at least a first and a second build-up welding portion along a bore of the cylinder block corresponding to the thrust and the anti-thrust directions, performing build-up welding in the first and the second build-up welding portions, and final finishing the cylinder block to the first finished bore dimension, whereby a surface of the bore retains an abrasion resistant layer having the abrasion resistance layer thickness and the desired welding strain along the thrust and anti-thrust directions.
According to another embodiment of the present invention, there is provided a method for manufacturing a cylinder block of an internal combustion engine, wherein: the first build-up welding portion is a first region aligned symmetrically to the thrust direction, and the second build-up welding portion is a second region aligned symmetrical to the anti-thrust direction, thereby providing abrasion resistance in a limited area capable of effectively meeting the set of parameters without damaging the internal combustion engine with excessive welding strain.
According to another embodiment of the present invention, there is provided a method for manufacturing a cylinder block of an internal combustion engine, wherein: the first region covers from at least about xc2x15xc2x0 to about xc2x185xc2x0 on either side of the thrust direction relative to a center axis of the bore, and the second region covers from at least about xc2x15xc2x0 to about xc2x185xc2x0 on either side of the anti-thrust direction relative to the center axis of the bore.
According to another embodiment of the present invention, there is provided a method for manufacturing a cylinder block of an internal combustion engine, wherein: the first region preferably covers from at least about xc2x15xc2x0 to about xc2x145xc2x0 on either side of thrust direction relative to the center axis of the bore, and the second region preferably covers from at least about xc2x15xc2x0 to about xc2x145xc2x0 on either side of the anti-thrust direction relative to the center axis.
According to another embodiment of the present invention, there is provided a method for manufacturing a cylinder block of an internal combustion engine, wherein: the step of defining a set of parameters includes a step of selecting a difference between the first finished bore dimension and at least a first recessed bore dimension, sufficient to allow the abrasion resistant layer to be from at least about 2 mm to about 5 mm in thickness, whereby the abrasion resistant layer is effective to resist abrasion during use and minimize distortion of the cylinder block due to the welding strain.
According to another embodiment of the present invention, there is provided a method for manufacturing a cylinder block of an internal combustion engine, wherein: the difference is preferably between from about 3 mm to about 4 mm.
According to another embodiment of the present invention, there is provided a method for manufacturing a cylinder block of an internal combustion engine, comprising the steps of: providing a preformed cylinder block having at least one preformed build-up welding portion along a cylinder bore matching at least a thrust direction, performing build-up welding in the at least one preformed build-up welding portion, and finishing the cylinder bore to a final form, whereby the surface of the cylinder bore is abrasion resistant in at least the thrust direction during operation of the internal combustion engine.
According to another embodiment of the present invention, there is provided a method for manufacturing a cylinder block of an internal combustion engine, wherein: the step of providing a preformed cylinder block includes a second step of providing the preformed cylinder block with at least a second preformed welding portion along the cylinder bore matching at least an anti-thrust direction, and the step of providing build-up welding includes a second step of providing the build-up welding in the second preformed welding portion.
According to another embodiment of the present invention, there is provided a method for manufacturing a cylinder block of an internal combustion engine, comprising the steps of: determining a set of parameters for the cylinder block, the set of parameters including at least a desired abrasion resistance layer thickness, a desired welding strain, a desired first finished bore diameter, a thrust direction, and an anti-thrust direction, forming a cylinder block matching the set of parameters and having at least a first recessed bore diameter greater than the first finished bore dimension, designating at least a first and a second build-up welding portion along a bore of the cylinder block corresponding to the thrust and the anti-thrust directions, performing build-up welding in the first and the second build-up welding portions, and finishing the bore into the first finished bore dimension, whereby a surface of the bore retains the desired abrasion resistance layer thickness along the thrust and the anti-thrust directions and the cylinder block has a first welding strain less than the desired welding strain.
According to another embodiment of the present invention, there is provided a method for manufacturing a cylinder block of an internal combustion engine, wherein: the desired abrasion resistance layer thickness is from at least about 2 mm to about 5 mm.
According to another embodiment of the present invention, there is provided a method for manufacturing a cylinder block of an internal combustion engine, wherein: the desired abrasion resistance layer thickness is preferably from at least about 3 mm to about 4 mm.
According to another embodiment of the present invention, there is provided a method for manufacturing a cylinder block of an internal combustion engine, wherein: the first build-up welding portion covers from at least about xc2x15xc2x0 to about xc2x185xc2x0 on either side of the thrust direction relative to a center axis of the bore, and the second build-up welding portion covers from at least about xc2x15xc2x0 to about xc2x185xc2x0 on either side of the anti-thrust direction relative to the center axis of the bore.
According to another embodiment of the present invention, there is provided a method for manufacturing a cylinder block of an internal combustion engine, wherein: the first build-up welding portion covers from at least about xc2x15xc2x0 to about xc2x145xc2x0 on either side of thrust direction relative to the center axis of the bore, and the second build-up welding portion from at least about xc2x15xc2x0 to about xc2x145xc2x0 on either side of the anti-thrust direction relative to a center axis.
According to another embodiment of the present invention, there is provided a method for manufacturing a cylinder block of an internal combustion engine, comprising the steps of: conducting build-up welding on an inner surface of a bore of the cylinder block only in a region where a detrimental abundance of piston abrasion occurs, and finishing the inner surface of the bore to a final dimension, whereby the inner surface is resistant to piston abrasion and a build-up welding portion has a desired final thickness.
According to another embodiment of the present invention, there is provided a method for manufacturing a cylinder block of an internal combustion engine, wherein: the region includes at least a first region from at least about xc2x15xc2x0 to about xc2x185xc2x0 in a thrust direction and a second region from at least about xc2x15xc2x0 to about xc2x185xc2x0 in an anti-thrust direction relative to the bore of the cylinder block.
According to another embodiment of the present invention, there is provided a method for manufacturing a cylinder block of an internal combustion engine, wherein: the inner surface is preformed into at least a first recessed shape along the thrust direction and at least a second recessed shape along the anti-thrust direction.
According to another embodiment of the present invention, there is provided a method for manufacturing a cylinder block of an internal combustion engine, wherein: the desired final thickness is from at least about 3 mm to about 4 mm in thickness.
The above, and other objects, features and advantages of the present invention will become apparent from the following description read in conjunction with the accompanying drawings, in which like reference numerals designate the same elements.